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Thursday, November 3, 2011

Solar Water and Space Heating Project With Unique Collector Design

Rob's new solar heating system provides both solar space and water heating. The system is based on the $1K drain back design, but incorporates a number of very interesting design variations that may be helpful if you are doing a system.

Rob's finished system with the two hizer design collectors.

Side view of the collectors.

One unique feature of Rob's system is that the collector uses the new hizer design. In most collectors the finned tubes that absorb solar radiation and transfer it to water flowing through the tubes run vertically with manifolds along the top and the bottom to supply water to the riser tubes at the bottom and collect heated water from the riser tubes along the top. The hizer design was invented by Alan Rushforth to provide a more efficient design for wide collectors. In the hizer design, the "riser" tubes run horizontally and the supply and return manifolds run vertically along the left and right sides. The resulting horizontal risers have been dubbed hizers. The hizer design results in shorter manifolds, and fewer riser to manifold connections -- a saving in both material and labor costs. I

Rob's collectors are the first ones I know of to use the hizer design in a drain back system. In order to insure that the collector water drains back to the storage tank (for freeze protection), all of the hizer runs are sloped slightly downward toward the supply manifold.

One of the collectors showing the hizer arrangement.

While Rob used two 10 ft wide hizer collectors, it would also be feasible to build a single 20 ft wide hizer collector. For large solar space heating applications that might now use 5 or 6 or more side by side 4 ft wide by 8 or 10 ft wide collectors that must all be installed separately and plumbed together, the hizer design offers the possibility to build one large collector in place with with 25 or more ft long horizontal hizers instead of many many vertical risers. It could be a real plus for wide, large site built collectors. In addition to the saving in time and material, it is believed that the hizer design will be easier to get even collector filling and flow.

This shows the vertical manifolds being laid out.

Rob did a very careful job of working out the structural and plumbing details for the system, and much can be learned by just going through the detailed construction pictures and seeing how Rob handled the various construction details.

For space heating distribution to the house, Rob will be using a water to air heat ex changer mounted in the furnace ducting. He plans to make some use of this same heat exchanger for summer cooling using well water.